Monitor for injection molding machine

ABSTRACT

Variables such as injection pressure and injection velocity are detected at a predetermined sampling cycle for each molding cycle and the variables for a plurality of past molding cycles starting from the latest molding cycle are stored. Change patterns of the stored variables of the respective molding cycles are displayed in the form of graphs in which the first axis represents time (the number of times of sampling), the second axis represents the variable values, and the third axis represents the molding cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of application Ser. No.10/749,374, filed Jan. 2, 2004, now pending, and claims the benefit ofJapanese Application No. 2003-006705, filed Jan. 15, 2003, of which thisapplication claims priority under 35 U.S.C. §120.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a monitor for monitoring a state ofmolding in an injection molding machine.

2. Description of the Related Art

States of various variables such as injecting velocity, injectingpressure, and the like during injection in an injection molding cyclecan be regarded as indicators of good or bad of a molding state.Therefore, the various variables during molding are sampled and graphedon a display and molding conditions are adjusted and evaluated andstability of molding is judged based on the graphs. Especially inevaluating the stability of the molding, waveforms are drawn one uponanother through a plurality of molding cycles so that how the waveformfluctuates through the respective cycles and cycle-to-cycle variation inthe waveform can be grasped.

In order to grasp how the waveform fluctuates and changes through themolding cycles, order of the drawn waveforms of the molding cycles needsto be judged. However, if the waveform graphs are drawn one uponanother, the waveforms overlap each other and it becomes difficult todiscriminate the changes in waveforms in the molding cycles from eachother. Therefore, there is a known method in which the latest waveformgraph and preceding waveform graphs are drawn in different colors todiscriminate the changes in the waveforms in the molding cycles overtime from each other (see Japanese Patent Application Laid-open No.2-26724, for example).

Moreover, there is also known art in which a shot number (molding cyclenumber) is designated on a horizontal axis (first axis), an injectionstart position or an amount of cushion is designated on a vertical axis(second axis), a lot is designated on a third axis, and relativerelationships between three kinds of monitoring data are displayed inthree dimensions (see Japanese Patent Application Laid-open No.2002-273773, for example).

In order to judge the stability of the molding state, it is preferablethat how the various variables change and vary over time in a singlemolding cycle can be grasped and also that the changes and variations inthe variables in the molding cycles can be observed and discriminatedfrom each other. In other words, it is preferable that changing andvarying patterns of the respective variables in the single molding cyclecan be grasped and that variations and changes in the patterns in theplurality of molding cycles can be discriminated from each other. In theabove-described prior-art method described in the above-mentionedJapanese Patent Application Laid-open No. 2-26724 in which the moldingwaveform patterns are displayed in different colors, the latest waveformpattern and the past waveform patterns can be discriminated from eachother based on the different colors because they are in differentcolors. However, the past waveform patterns are in the same color andboth the past waveform patterns and the latest waveform pattern aredrawn one upon another. Therefore, the waveform patterns overlap eachother and it is difficult to discriminate variations, changes, andtrends in the variations in the waveform patterns from each other.

In the method described in the above-mentioned Japanese PatentApplication Laid-Open No. 2002-273773, the waveform patterns in lots canbe compared with each other to grasp differences between the lots.However, it is impossible to grasp how the variable varies and how awaveform pattern varies and changes in a single molding cycle and tojudge stability of molding.

SUMMARY OF THE INVENTION

According to the present invention, a monitor for an injection moldingmachine comprises sampling means for detecting, at every predeterminedcycle, a variable varying in one molding cycle in an injection moldingprocess and storing the detected variable; and means for displaying thechange pattern of the variable for a plurality of molding cycles in theform of three dimensional graphs using three axes.

According to a first aspect of the invention, the displaying meansdisplays the variable for the plurality of molding cycles in the form ofgraphs in which a first axis represents time, a second axis representsthe variable and a third axis represents the number of molding cycles.

According to a second aspect of the invention, the sampling meansdetects, at every predetermined cycle, at least the position of amovable member and one or more other variables and stores thesevariables, and the displaying means displays the variables for aplurality of molding cycles in the form of graphs in which a first axisrepresents the position of the movable member, a second axis representsthe above-mentioned other variables and a third axis represents thenumber of molding cycles.

According to a third aspect of the invention, the monitor furthercomprises means for storing a time at a predetermined timing in eachmolding cycle. And, the displaying means displays the variable for aplurality of molding cycles in the form of graphs in which a first axisrepresents time, a second axis represents the variable and a third axisrepresents the time.

According to a fourth aspect of the invention, the monitor furthercomprises means for storing a time at a predetermined timing in eachmolding cycle. The sampling means detects, at every predetermined cycle,at least the position of a movable member and one or more othervariables and stores these variables. And, the displaying means displaysthe variables for a plurality of molding cycles in the form of graphs inwhich a first axis represents the position of the movable member, asecond axis represents the variables and a third axis represents thetime.

The first to fourth aspects of the invention may adopt the followingforms.

The sampling means is provided in the injection molding machine (e.g.,in a controller) or in an external device (e.g., a computer) connectedto the injection molding machine.

The graphically displaying means is provided in the injection moldingmachine (e.g., in a controller) or in an external device (e.g., acomputer) connected to the injection molding machine.

The variable is a difference between a sampled variable and a referencevariable which is a variable in a specific molding cycle.

The variables varying in one molding cycle in the injection moldingprocess include one of injection pressure, injection velocity, a screwposition, screw rotation speed, back pressure, motor torque, a moldopening/closing position/speed, an ejector position/speed, andtemperatures of a cylinder or a nozzle.

According to the invention, there is provided the monitor of theinjection molding machine which can judge molding states includingstability of molding.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the embodiments byreference to the drawings in which:

FIG. 1 is a block diagram of an essential portion of a controller of aninjection molding machine, which forms a monitor in each embodiment ofthe invention, and an essential portion of the injection moldingmachine;

FIG. 2 is a flow chart of monitor data obtaining processing in a firstembodiment of the invention;

FIG. 3 is an explanatory view of a table in which the sampling dataobtained by the processing in FIG. 2 are stored;

FIG. 4 is a flow chart of displaying processing of the sampling datastored in the table in FIG. 3;

FIG. 5 shows an example of a screen on which monitor data are displayedby the displaying processing in FIG. 4;

FIG. 6 is a flowchart of monitor data obtaining processing in a secondembodiment of the invention;

FIG. 7 is an explanatory view of a table in which the sampling dataobtained by the processing in FIG. 6 are stored;

FIG. 8 shows an example of a screen on which sampling data stored in thetable in FIG. 7 are displayed;

FIG. 9 is a flowchart of monitor data obtaining processing in a thirdembodiment of the invention;

FIG. 10 is an explanatory view of a table in which the sampling dataobtained by the processing in FIG. 9 are stored;

FIG. 11 shows an example of a screen on which sampling data stored inthe table in FIG. 10 are displayed;

FIG. 12 is a flow chart of monitor data obtaining processing in a fourthembodiment of the invention;

FIG. 13 is an explanatory view of a table in which the sampling dataobtained by the processing in FIG. 12 are stored;

FIG. 14 shows an example of a screen on which sampling data stored inthe table in FIG. 13 are displayed;

FIG. 15 shows an example in which the monitor for the injection moldingmachine according to the invention is provided in the controller for theinjection molding machine;

FIG. 16 shows an example in which sampling means of the monitor for theinjection molding machine according to the invention is provided in thecontroller for the injection molding machine and sampling data storagemeans and graph displaying means of the monitor are provided in apersonal computer; and

FIG. 17 shows an example in which the monitor for the injection moldingmachine according to the invention is provided in a personal computerconnected to the injection molding machine.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a block diagram of an essential portion of a controller of aninjection molding machine, which forms a monitor in each embodiment ofthe invention, and an essential portion of the injection molding machine

A reference numeral 1 designates an injection cylinder of the injectionmolding machine and 2 designates a screw. The screw 2 is driven in adirection of an injection axis by an injection servo motor M1 through adriving converter 5 for converting a rotational motion into a linearmotion in the direction of the injection axis and is rotated formetering by a screw rotating servo motor M2 through a transmissionmechanism 3. A pressure detector 4 is provided at a base portion of thescrew 2 to detect pressure of resin acting in an axial direction of thescrew 2, i.e., injection pressure in an injection process and screw backpressure in metering and kneading process. The injection servo motor M1is provided with a position/velocity detector P1 such as an encoder fordetecting a position of the screw 2 and an injection velocity which is avelocity of movement of the screw 2. The screw rotating servo motor M2is provided with a speed detector P2 for detecting a rotation speed ofthe screw 2.

The controller 10 of the injection molding machine includes a CNC CPU 25which is a microprocessor for numerical control, a PMC CPU 18 which is amicroprocessor for a programmable controller, a servo CPU 20 which is amicroprocessor for servo control, and a pressure monitoring CPU 17 of amicroprocessor for sampling injection pressure and screw back pressurethrough an A/D converter 16. By selecting mutual input and output via abus 22, information can be conveyed between the respectivemicroprocessors.

To the PMC CPU 18, a ROM 13 for storing a sequence program forcontrolling a sequence operation of the injection molding machine, aprogram for monitor data displaying processing, and the like and a RAM14 used for temporarily storing operation data and the like areconnected. On the other hand, to the CNC CPU 25, a ROM 27 for storing aprogram for controlling the whole injection molding machine and the likeand a RAM 28 used for temporarily storing operation data and the likeare connected.

To the servo CPU 20 and the pressure monitor CPU 17, a ROM 21 forstoring a control program written specifically for servo control, a RAM19 for temporarily storing data, a ROM 11 for storing a control programrelated to sampling processing for obtaining pressure data and the like,and a RAM 12 used for temporarily storing data are connected.Furthermore, to the servo CPU 20, a servo amplifier 15 for driving servomotors of respective axes for mold clamping, an ejector (not shown),injection, and screw rotation based on a command from the CPU 20 isconnected. Respective outputs from the position/velocity detector P1provided to the injection servo motor M1 and the speed detector P2provided to the screw rotating servo motor M2 are fed back to the servoCPU 20. A current position and the injection velocity (screw movingvelocity) of the screw 2 calculated by the servo CPU 20 based on afeedback signal from the position/velocity detector P1 and a rotationspeed of the screw 2 detected by the speed detector P2 are stored in acurrent position storage register and a current velocity storageregister provided to the RAM 19.

To an interface 23, an external personal computer and the like can beconnected. A manual data input unit 29 with a display is connected tothe bus 22 via a CRT display circuit 26 to select a monitor displayscreen and a function menu item and to carry out input operation ofvarious data and is provided with numerical keys for inputting numericaldata, various function keys, and the like.

A RAM 24 for storing molding data is formed of nonvolatile memory andstores molding conditions (injection/dwell conditions, meteringconditions, and the like), various set values, parameters, macrovariables, and the like related to injection molding operation.

With the above structure, the CNC CPU 25 distributes pulses to the servomotors of the respective axes based on a control program of the ROM 27and the servo CPU 20 carries out servo controls such as a position loopcontrol, a velocity loop control, a current loop control, and the likesimilarly to the prior art to execute so-called digital servo processingbased on movement commands pulse-distributed to the respective axes anda feedback signal of a position and a feedback signal of a speeddetected by detectors such as the pulse coder P1 and the speed detectorP2.

In the present embodiment, the pressure monitor CPU 17 repeatedlyexecutes sampling processing in every injection/dwell process, readsinjection pressure acting on the screw 2 through the pressure detector 4and the A/D converter 16, and reads an injection velocity and a screwposition stored in the current velocity storage register and the currentposition storage register of the memory 19 to store them in the RAM 12.

FIG. 2 is a flow chart of monitor data obtaining processing performed bythe pressure monitor CPU 17 in the first embodiment. In this embodiment,an injection pressure PR and an injection velocity V are detected asmonitor data at every predetermined sampling cycle.

If operation starts, a shot counter S for counting the number of moldingcycles (number of shots (injections)) at “0” (step 100). If theinjection starts (step 101), a sampling counter t for counting thenumber of sampling is set at “0” (step 102) and whether dwell processhas finished or not is judged (step 103). If dwell process has not beenfinished, a current injection pressure PRa detected from a load cell anda current injection velocity Va detected from the position/velocitydetector are respectively stored in a table provided in the RAM 12 as PR(S, t) and V (S, t), respectively, in association with values of theshot counter S and the sampling counter t (step 104).

The table provided in the RAM 12 is a table for cyclically storingsampling data of (m+1) times molding cycles as shown in FIG. 3 andstores the sampling data in accordance with the shot counter S.

Next, the sampling counter t is incremented by 1 (step 105) and theprocessing returns to step 103. From then on, the processings from steps103 to 105 are repeatedly executed at every predetermined sampling cycleuntil the dwell process ends and the sampled injection pressure PR (S,t) and injection velocity V (S, t) are stored in the table as shown inFIG. 3.

If the dwell process ends, whether an operation end command has beeninput or not is judged (step 106). If the operation is not ended, theshot counter S is incremented by 1 (step 107) and whether or not thevalue of the shot counter S is greater than a set number m to be storedis judged (step 108). If the value is not greater than the set number,the processing returns to step 101. On the other hand, if the value isgreater than the set number m, the shot counter S is set at “0” (step109) and the processing returns to step 101.

From then on, the above processings from step 101 to 109 is repeatedlyexecuted until the operation ends. Thus, the injection pressure PR (S,t) and the injection velocity V (S, t) which are sampling data forrespective shots are cyclically stored for (m+1) times molding cycles inthe table as shown in FIG. 3.

On the other hand, if a monitor display command is input, the PMC CPU 18executes display processing in FIG. 4 at every predetermined cycle.

First, whether or not a value of a pointer P agrees with the shotcounter S is judged (step 200). This is for judging whether or not thepointer P is pointing a molding cycle at which sampling data is beingtaken currently. If the value agrees with the shot counter S, that meansthe sampling data is being rewritten. In consequence, the processing ofthis cycle is finished. If the value does not agree with the shotcounter S, the value of the shot counter S is stored in the pointer Pand an index i is set at the set number m (step 201).

Next, 1 is added to the pointer P and the index i is decremented by 1(step 202). Whether or not the value of the pointer P has exceeded theset number m as a result of the processing at step 202 is judged (step203). If the value is greater than the set value m, “0” is set to thepointer P (step 204) and the processing proceeds to step 205. If thevalue of the pointer P is not greater than the set value m, theprocessing proceeds from step 203 to step 205. By this processing, theoldest stored sampling data is designated.

In step 205, as shown in FIG. 5, in a coordinate system in which time isdesignated on a first axis, injection pressure and injection velocityare designated on a second axis, and the molding cycle number (shotnumber) is designated on a third axis, sampling data of the injectionpressure and injection velocity pointed by the pointer P are plotted ata position on the third axis, which represents cycle number (shotnumber) indicated by the index i, in association with the samplingnumber (time) on the first axis and are graphically displayed (step205). In this case, the injection pressure and the injection velocityare displayed in a solid line and a broken line or in difference colorsas shown in FIG. 5 so that the graphs of the injection pressure and theinjection velocity can be distinguished from each other.

Then, whether the value of the index i is “0” or not is judged (step206). If it is not “0”, the processing returns to step 202. From thenon, the processings from step 202 to step 206 are repeatedly executeduntil the value of the index i becomes “0”. Then, when the value of theindex i becomes “0”, sampling data displaying processing finishes.

By the above-described-processing, sampling data at a molding cyclewhich is m cycles before a current shot in which injection is inprogress and sampling data are being obtained are graphically displayedat a position of (m−1) on the third axis and sampling data at a moldingcycle (shot) immediately before the current cycle (shot) are graphicallydisplayed at a position of “0” (i=0) on the third axis.

For example, if m=5, sampling data of 6 molding cycles from S=0 to 5 areto be cyclically stored in the table, and the value of the shot counterS is “2”, the sampling data of P=P+1=S+1=2+1=3 stored in the table arethe oldest sampling data of a shot which is m cycles before a currentone and these sampling data are first displayed at a position ofi=m−1=5−1=4. Then, because the pointer P is incremented by 1 and theindex i is decremented by 1 in step 202, sampling data of P=4(=S) arenext displayed at a position of i=3 on the third axis and then samplingdata of P=5(=S) are displayed at a position of i=2 on the third axis.Next, because P=6 at step 202, P=0 by steps 203 and 204 and samplingdata of P=0 (=S) are displayed at a position of i=1 on the third axis.Lastly, sampling data of P=1 (=S) are displayed at a position of i=0 onthe third axis.

In the above manner, from sampling data of S=4 pointed by the pointerP=4 and which are currently being rewritten, stored sampling data aredisplayed in an order from the oldest one to later ones in positions ofi=4, 3, 2, 1, and 0 on the third axis.

Thus, when graphic display of the m sampling data stored in the table,excluding the sampling data which is currently being written, ends, theprocessing proceeds from step 206 to step 207 where the pointer P isincremented by 1 to finish the processing at the present cycle. Byincrementing the pointer P by 1, the value of the pointer P becomesequal to a current value of the shot counter S indicating a shot inwhich sampling data are currently being rewritten.

Then, if obtaining of the sampling data has finished, the value of theshot counter S is rewritten by the processings at steps 107 and 109 inFIG. 2, and the value of the pointer P does not agree with the value ofthe shot counter S at step 200, the processings in step 201 and thefollowing steps are executed again and sampling data in the latest mshots are graphically displayed as shown in FIG. 5.

In FIG. 5, the injection pressure PR and the injection velocity V, whichare variables in the molding cycle, are graphically displayed of changepatterns with respect to time and it is possible to easily grasp how thevariable varies and changes in each the molding cycle by using singlechange pattern. Moreover, because the change patterns of the variable ofthe respective molding cycles are drawn in parallel to each other in adirection of the third axis, it is possible to easily graspcycle-to-cycle variation in the change pattern of the variable and toeasily judge stability of molding.

FIG. 6 is a flow chart of sampling data obtaining processing in a secondembodiment of the invention. The second embodiment is different from thefirst embodiment in that a screw position PO is also sampled as monitordata.

If comparison is made between the sampling data obtaining processingshown in FIG. 6 and the sampling data obtaining processing in the firstembodiment shown in FIG. 2, steps 300 to 309 correspond to steps 100 to109 and processing in FIG. 6 is the same as that in FIG. 2 except thatprocessing at step 304 and processing at step 104 are different fromeach other. In the second embodiment, the screw position POa stored inthe current position storage register of RAM 19 is also obtained at step304 where data is obtained. The injection pressure PRa, the injectionvelocity Va, and the screw position POa are obtained at everypredetermined sampling cycle and stored in a table provided to the RAM12 and shown in FIG. 7.

Because the screw position POa is merely added as the sampling data ascompared with the first embodiment, detailed description of theprocessing shown in FIG. 6 will be omitted.

Although monitor data displaying processing in the second embodiment ismostly similar to the displaying processing in the first embodimentshown in FIG. 4, the processing at step 205 is different and the otherprocessings are the same.

Although the first axis represents time (the number of times ofsampling) in the processing at step 205 in the first embodiment, thefirst axis is displayed as an axis representing the screw position PO inthe second embodiment. As shown in FIG. 8, the first axis represents thescrew position PO, the second axis represents the injection pressure PRand the injection velocity V, and the third axis represents the moldingcycle number, i.e., the shot number. Then, the injection pressure PR andthe injection velocity V corresponding to the screw position PO in eachsampling at every molding cycle (shot) and stored in the table shown inFIG. 7 are plotted, and patterns of the injection pressure and theinjection velocity corresponding to the screw position are displayed sothat the later molding cycle (shot) is closer to the front (closer to anorigin point of the coordinate system) as shown in FIG. 8.

FIG. 9 is a flowchart of sampling data obtaining processing in the thirdembodiment of the invention. In the third embodiment, data to beobtained as sampling data are injection pressure PR and injectionvelocity V at every shot and are similar to those in the firstembodiment. However, the third embodiment is different from the firstembodiment in that a time of a predetermined timing (for example, timewhen dwell process ends) in the molding cycle is stored. In other words,if comparison is made between the flow chart of the sampling dataobtaining processing shown in FIG. 9 and the flow chart of the firstembodiment and shown in FIG. 2, it is apparent that the third embodimentis different from the first embodiment only in that a time Ta is storedin a reading table at step 406 after dwell process has finished. Theother processings are the same.

Then, in the third embodiment, the injection pressure PR, the injectionvelocity V and the time T at every predetermined sampling cycle arestored at every shot in the table as shown in FIG. 10.

Although the monitor data displaying processing in the third embodimentis mostly similar to the displaying processing in the first embodimentshown in FIG. 4, the processing at step 205 is different and the otherprocessings are the same. In the third embodiment, as shown in FIG. 11,a first axis represents the sampling time, a second axis represents theinjection pressure PR and the injection velocity V, a third axisrepresents a dwell end time T in each the molding cycle, and patterns ofthe injection pressure PR and the injection velocity V with respect totime are drawn at a position on the third axis corresponding to thedwell end time T stored in the table.

In a case of the third embodiment, in the processing at step 205, aposition corresponding to a value obtained by subtracting a time of thepresent molding cycle stored in the table from a current time is theposition on the third axis (position of i at step 205) where thesampling data in the molding cycle are drawn.

FIG. 12 is a flow chart of sampling data obtaining processing in thefourth embodiment of the invention. The fourth embodiment is differentfrom the third embodiment only in that the screw position PO is alsoobtained as sampling data. In other words, only processing at step 504is different from the processing at step 404. Because the otherprocessings are the same, description of the processing shown in FIG. 10will be omitted.

In a case of the fourth embodiment, the injection pressure PR, theinjection velocity V, the screw position PO, and the dwell end time Tatevery sampling time are stored at every molding cycle (every shot) inthe table provided to the RAM 12 as shown in FIG. 13.

In the monitor data displaying processing in the fourth embodiment, thefirst axis represents the screw position, the second axis represents theinjection pressure PR and the injection velocity V, the third axisrepresents the dwell end time Tin each molding cycle as shown in FIG.14, and the injection pressure PR and the injection velocity V areplotted at a position on the third axis corresponding to the dwell endtime T stored in the table, in association with the screw position PO,so that the patterns of the injection pressure PR and the injectionvelocity V with respect to the screw position PO are drawn.

Although the variables (such as injection pressure, injection velocity,screw position) are detected at each molding cycle and graphicallydisplayed in the above-described respective embodiments, it is alsopossible to store the sampling data of the variables of one moldingcycle in the table at every predetermined number of molding cycles andat intervals of the predetermined number of molding cycles and todisplay the graphs based on the stored data and at intervals of thepredetermined number of molding cycles. If the data are displayed forevery process such as injection, dwell, metering, and the like, timingsof storing times are preferably start time or end time of each theprocess and it is possible to automate selection of the timing.Moreover, it is possible that the monitor data obtaining processing isstarted and finished by operation by an operator.

Although data to be sampled as monitor data are injection pressure,injection velocity, screw position and dwell end time in theabove-described embodiment, it is also possible that other variablessuch as screw rotation speed, back pressure, motor torque, moldopening/closing position/speed, ejector position/speed, and temperaturesof a cylinder and a nozzle are sampled as monitor data and displayed inthree dimensions as described above. The timings of storing times may bewhen the injection starts, the cycle starts, or closing of the moldstarts. Furthermore, as a time to be stored, not only a time obtainedfrom a clock but also a time which has elapsed from a specific time suchas a time of turning on of the power may be used.

In displaying, it is possible that the displayed three-dimensionalcoordinate system can be rotated.

Moreover, a variable in a specific cycle may be employed as a referencevariable and the variable displayed as a graph may be a differencebetween a sampled variable and the reference variable. For example, ifthe reference specific cycle is the oldest cycle in the stored cyclesand a variable in this cycle is employed as a reference variable, areference pointer for pointing the reference cycle is provided and “S+1”is stored in the pointer to set the oldest cycle in the stored cycles atstep 201 in FIG. 4 (“0” is stored in the reference pointer when S+1 isgreater than the set number m). Then, at step 205, a difference isobtained by subtracting a variable of corresponding sampling data in acycle stored in the reference pointer from sampling data in the cyclepointed by the pointer P and this difference may be displayed.

It is also possible that a variable of sampling data at a specific cycleemployed as a reference cycle is set as reference data and stored inadvance and that a difference between a variable at each sampling and acorresponding variable at the reference sampling is obtained anddisplayed, at step 205.

In the above-described embodiment, the monitor is formed of a controller10 itself of the injection molding machine and all of means A forsampling respective variables x, means B for displaying graphs, andmeans C for storing variable data sampled at each molding cycle (shot)are provided in the controller for controlling an injection moldingmachine. Schematic illustration of this form is as shown in FIG. 15.

On the other hand, it is also possible that the means A for sampling thevarious variables x is provided in the controller 10 of the injectionmolding machine and that the means C for storing the sampling data andthe means B for displaying the graphs are provided in a personalcomputer 50 so as to perform processings such as summarization andediting of the sampled data. FIG. 16 is a schematic diagram of thisform.

In a case of this form, the personal computer 50 is connected throughthe interface 23 provided to the controller 10 of the injection moldingmachine. The pressure monitor CPU 17 forming the sampling means Asamples the variables (such as injection pressure and injectionvelocity) at each molding cycle (shot), stores them in the RAM 12, andtransfers them every time the molding cycle (shot) ends or transfersdata for the predetermined number of shots at a time at everypredetermined number of shots to the personal computer 50 through theinterface 23. On the other hand, the personal computer 50 is providedwith the table as shown in FIGS. 3, 7, 10, and 13 and stores thereceived sampling data of the various variables x for each the moldingcycle. Then, the personal computer 50 displays the stored sampling datain three dimensions. By employing the form shown in FIG. 16, samplingdata of various variables x in a plurality of injection molding machinesmay be stored in a concentrated manner in storage means provided to acomputer of a central controller and the sampling data of the respectiveinjection molding machines may be graphically displayed so that moldingstates of a plurality of injection molding machines can be monitored ina concentrated manner.

Furthermore, as shown in FIG. 17, it is also possible that the samplingmeans A, the graph displaying means B, and the storage means C forstoring the sampling data are provided to the personal computer. In thiscase, means for detecting variables of the injection molding machine andthe personal computer 50 need be connected to each other. For example,if injection pressure PR, injection velocity V and screw position PO areto be sampled as variables x, a pressure detector 4 and aposition/velocity detector P1 are connected to a personal computer 50and the injection pressure PR, the injection velocity V and the screwposition PO, detected by these pressure detector 4 and theposition/velocity detector P1, are detected by the personal computer 50at every predetermined cycle, stored in the storage means as in theabove-described first to fourth embodiments, and graphically displayed.

As described above, according to the present invention, variousvariables indicating molding states at respective molding cycles aregraphically displayed as waveforms with respect to time and screwposition, along an axis representing the molding cycle, in threedimensions. As a result, it is possible to easily and visually grasp howthe change patterns of variables (change waveforms of variables) varythrough the molding cycles. Therefore, it is easy to judge the stabilityof the molding.

1. A monitor for an injection molding machine, comprising: samplingmeans for detecting, in each of successive molding cycles a moldingcycle variable, varying in each molding cycle in an injection moldingprocess, and storing the detected variable; means for storing an end ofcycle time for each molding cycle; and means for graphically displayingthe detected variables for a plurality of molding cycles, with a firstaxis representing time, a second axis representing said detectedvariables and a third axis representing said molding cycles.
 2. Themonitor for an injection molding machine according to claim 1, whereinthe sampling means is provided in the injection molding machine.
 3. Themonitor for an injection molding machine according to claim 1, whereinthe sampling means is outside the injection molding machine andconnected to the injection molding machine.
 4. The monitor for aninjection molding machine according to claim 1, wherein said graphicallydisplaying means is provided in the injection molding machine.
 5. Themonitor for an injection molding machine according to claim 1, whereinsaid graphically displaying means is outside the injection moldingmachine and connected to the injection molding machine.
 6. The monitorfor an injection molding machine according to claim 1, wherein saidvariable is a difference between a sampled variable and a referencevariable which is a variable in a specific molding cycle.
 7. The monitorfor an injection molding machine according to claim 1, wherein thevariable varying in one molding cycle in the injection molding processincludes one of injection pressure, injection velocity, a screwposition, screw rotation speed, backpressure, motor torque, a moldopening or closing position, a mold opening or closing speed, an ejectorposition or speed, and temperatures of a cylinder or a nozzle.